Ethanol is a transportation fuel commonly blending into gasoline. Cellulosic material is used as a feedstock in ethanol production processes. There are several processes in the art for making cellulose and hemicelluloses hydrolysates containing glucose, mannose, xylose and arabinose. Glucose and mannose are efficiently converted to ethanol during natural anaerobic metabolism. By far the most efficient ethanol producing microorganism is the yeast Saccharomyces cerevisiae. However, Saccharomyces cerevisiae lacks the necessary enzymes to convert the dominant sugar xylose into xylulose and is therefore unable to utilize xylose as a carbon source. To do so requires genetic engineering of Saccharomyces cerevisiae to express enzymes that can convert xylose into xylulose. One of the enzymes needed is xylose isomerase (E.C. 5.3.1.5) which converts xylose into xylulose, which can then be converted into ethanol during fermentation by Saccharomyces cerevisiae. 
WO 2003/062430 discloses that the introduction of a functional Piromyces xylose isomerase (XI) into Saccharomyces cerevisiae allows slow metabolism of xylose via the endogenous xylulokinase (EC 2.7.1.17) encoded by XKS1 and the enzymes of the non-oxidative part of the pentose phosphate pathway and confers to the yeast transformants the ability to grow on xylose.
U.S. Pat. No. 8,586,336-B2 disclosed a Saccharomyces cerevisiae yeast strain expressing a xylose isomerase obtained by bovine rumen fluid. The yeast strain can be used to produce ethanol by culturing under anaerobic fermentation conditions.
Despite significant improvement of ethanol production processes from cellulosic material over the past decade there is still a desire and need for providing improved processes. To produce ethanol economically a fermentation organism that is biologically efficient is required.